This invention relates generally to elongate medical devices insertable into the body, which are provided with optical viewing apparatus by which a remote site within the body near the distal extremity of the device can be seen from outside the body. Particularly, the invention relates to medical devices insertable into the body by way of a natural body opening, which are provided with optical viewing apparatus and with means, situated near the distal extremity and manipulable from the proximal extremity, for treatment of an internal organ. Such devices include for example transurethral catheter devices for treatment of the prostate.
Conventionally the distal extremity of such a device is introduced into the body and is maneuvered remotely, by manipulation of controls outside the body, to the site within the body that is to be observed and treated. Optical viewing apparatus in such devices typically provides for illumination of part of the region near (typically forward of) the distal extremity, and for conducting an image from the distal extremity to the proximal extremity, where the operator can view it.
Transurethral needle ablation devices having optical viewing capability and designed for treating the tissue of the prostate are described for example in U.S. Pat. Nos. 5,370,675; 5,366,490; and 5,435,805; and International Patent Publication No. WO 96/22739. The optical viewing apparatus in these devices facilitates positioning the distal extremity of the device at the appropriate site within the urethra, by illuminating the interior of the urethra and providing the operator with an image of the urethra wall as the distal extremity of the device is advanced within it toward the treatment site.
Many such procedures entail application of high-frequency electrical current, microwave energy, radio frequency energy, acoustical energy or laser energy to destroy cells in a target tissue. Significant damage to adjacent or surrounding tissues can result from application of the treatment if the treatment means is not precisely positioned before the ablating energy is applied. In a transurethral needle ablation procedure for treatment of the prostate, for example, when the needle electrode is pressed against the urethral wall the tip of the needle may fail to puncture the urethral wall, so that even when the needle is fully deployed it has not crossed into the prostate tissue. Application of electrical energy under these circumstances can result in severe trauma to the urethra.
Accordingly, in some disclosed devices, the optical viewing apparatus is additionally intended to address both a need to observe the progress of the distal extremity of the device to the treatment site, and a need to be able to view the treatment means while the treatment is in progress.
For example, U.S. Pat. No. 5,435,805 is directed to a device (such as a device for treatment of benign prostate hypertrophy) having optical viewing capability for precise placement of the device which delivers the therapeutic energy into targeted tissues while minimizing effects on surrounding tissue. Particularly, U.S. Pat. No. 5,435,805 discloses a medical probe device having a stylet guide housing with at least one stylet port and means for directing a flexible stylet sideways out through the port into a target tissue, and a fiber optic viewing assembly, which has a viewing field extending forwardly and sidewardly of the guide housing to permit viewing of the stylet as it is deployed sideways from the distal extremity of the guide housing. To provide an unobstructed view of the emerging stylet, in some embodiments a portion of the material of the guide housing is removed to form a transverse depression behind the stylet port. However, the urethral wall is flabby, and tends to collapse into the depression, obscuring the view forward. In other embodiments the guide housing is provided with a window; but such an arrangement is difficult to manufacture and provides only limited visibility.